As is well known, all hydrocarbon wells require completion, and most wells require re-completion or workover. It is also well known that these operations are preferably performed without killing the well. Most completion, re-completion and workover operations require that a high-pressure mandrel or tubing, often with attached downhole tool(s), be stroked into or out of a wellhead or a wellbore while downhole fluids under pressure are controlled. In order to ensure that the well fluids do not escape to atmosphere, well control equipment such as blowout preventers (BOPs) must be used to control the well while a rig, jacks or hydraulic cylinders are used to move the high-pressure mandrel or tubing as desired. Although stacks of two or more BOPs can be used to control a well when tubing and/or downhole tool(s) are being inserted into or removed from a well, it is often more economical to use a “snubber spool” in conjunction with a single BOP for well control.
A snubber spool, also referred to as an “anchor spool”, is described in Assignee's U.S. Pat. No. 7,210,525 which issued on May 1, 2007 and is entitled Apparatus For Controlling A Tool Having A Mandrel That Must Be Stroked Into Or Out Of A Well, the entire specification of which is incorporated herein by reference.
FIG. 1 is an isometric view of the snubber spool 10 described in Applicant's above-identified United States patent. Affixed to the snubber spool 10 is a base plate 12 that supports a superstructure 30 (FIG. 1A) used to stroke the high-pressure mandrel, tubing, and/or downhole tool(s) connected to the tubing into or out of a wellbore. The base plate 12 is generally oriented at right angles to a port 24 that is used to balance well fluid pressure or to bleed well fluid pressure from the snubber spool 10. The base plate 12 is permanently affixed to the snubber spool 10 and is strengthened and supported by gussets 14a, 14b, which are welded to an outer sidewall 20 of the snubber spool 10 and to a top surface of the base plate 12. To further strengthen the base plate 12, optional gussets 16a, 16b may be welded to the outer sidewall 20 and the bottom surface of the base plate 12. The base plate 12 includes through bores 18a, 18b which receive rod ends 40a, 40b (FIG. 1a) of the superstructure 30 to detachably connect the superstructure 30 to the snubber spool 10.
The pressure balance/bleed port 24 is controlled by a shutoff valve 25. Lifting eyes 26a, 26b provide convenient attachment points for lifting the snubber spool 10 on to or off of a wellhead, truck or the like. A top end 28 of the snubber spool 10 is configured as required to provide a fluid seal around a tubing or mandrel to be stroked into or out of a wellhead or a wellbore, and to provide a connection for a wellhead isolation tool or any one of many adapters known in the art. In this embodiment the top end of the snubber spool 10 is configured for a threaded connection, but the top end 28 may also terminate in a flange, a Grayloc® connector, or the like.
The superstructure 30 shown in FIG. 1A includes a top plate 32 to which a cylinder end of first and second hydraulic cylinders or screw jacks, 34a, 34b are affixed by end caps 42a, 42b. A through bore 44 in the top plate 32 provides a fluid flow path through the top plate 32. An adapter, a swivel, or the like is connected to opposite sides of the top plate in fluid communication with the through bore 44, depending on the job for which the snubber spool 10 is being used. The rod ends 36a, 36b of the hydraulic cylinders or screw jacks 34a, 34b are provided with stop collars 38a, 38b that support the superstructure 30 when the threaded rod ends 40a, 40b are inserted through the respective bores 18a, 18b in the base plate 12 and suitable fasteners (not shown) are connected to the threaded rod ends 40a, 40bto lock the superstructure 30 to the base plate 12.
Alternatively, the superstructure 30 may be connected to the base plate 12 using a quick-connect system shown in FIG. 1b. The quick-connect system includes a wing adapter 42 threadedly connected to the threaded rod ends 40a, 40b (only 40b is shown).The wing adapter 42 is threadedly connected to a quick-connect anchor pin 45 received in a through bore 18c in the base plate 12. The quick-connect anchor pin 45 is secured to the base plate 12 by an anchor nut 46 that engages a pin thread 48 on an outer periphery of the quick-connect anchor pin 55 above the base plate 12. A hammer nut 50, rotatably supported by the wing adapter 42 engages a pin thread 52 on a top end of the quick-connect anchor pin 45 to detachably lock the rod ends 36a, 36b (only 36b is shown) to the quick-connect anchor pin 45. The hammer nuts 50 are used to quickly connect the superstructure 30 to the base plate 12 and release the superstructure 30 from the base plate 12.
While the snubber spool 10 has proved very useful and commercially successful, the base plate 12 interferes with free movement around the wellhead and complicates handling and transportation of the snubber spool 10.
Therefore there exists a need for a snubber spool with a detachable base plate that can be readily removed when the base plate is not in use.